Heat sealer for stretch wrapping apparatus

ABSTRACT

A heat sealing device for sealing layers of plastic film together is provided. In a preferred embodiment, the heat sealing device is incorporated into a stretch wrapping apparatus for wrapping a load. The heat sealing device includes a heater element, an air compressor or blower, and a sealing head in fluid communication with the heater element to distribute the heated air. The sealing head is preferably flexible and includes a plurality of convection ports configured to apply heated air to a portion of the packaging material without being completely covered by the packaging material. At least one insulated film contact portion is provided to distance the convection ports from the plastic film.

[0001] This application claims priority under 35 U.S.C. § 119 based onU.S. Provisional Application No. 60/292,521, filed May 23, 2001, thecomplete disclosure of which is incorporated herein by reference.

DESCRIPTION OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to wrapping a load with packaging material,and, more particularly, to stretch wrapping.

[0004] 2. Background of the Invention

[0005] Stretch wrapping can be performed as an inline automatedpackaging technique which dispenses and wraps packaging material in astretched condition around a load on a pallet to cover and contain theload. Pallet stretch wrapping, whether accomplished by turntable,overhead arm, or rotating ring typically covers the four vertical sidesof the load with a stretchable film such as polyethylene film. After thesides of the load are covered, the web of film is cut and the tail isusually “wiped” to press it against the load. Most stretch wrappackaging films are manufactured with an element of tackiness to add totheir layered stability and to provide a mechanism for closure of theending film tail, however, wiping is not sufficient to ensure that thetail of the film will not come loose during shipping, resulting in looseor torn wrap. In addition, in certain circumstances, such as outsidestorage of loads, open truck transit where winds can cause unwinding offilm, or where tacky film is undesirable or unavailable, merely wrappingthe load will not protect it. To overcome these problems, the tail ofthe packaging material can be adhered to the wrapped load by heatsealing. Sealing plastic wrapping material with heat, however, posesanother set of problems.

[0006] Many types of plastic films are effectively sealed for thepurpose of making a bag, closing a bag, or completing the enclosure of apackage wrapped in film. The most popular plastic films include high andlow density polyethylene, irradiated polyethylene, polypropylene, PVCand EVA. Technology for sealing each of these films is well known in theart. Unlike most other packaging films, low-density polyethylene has asealing temperature very close to its melt temperature. As a result,great care must be taken to insure there are no unsupported strains onthe film while the film is substantially melted during the sealingprocess. Most successful sealing of polyethylene is accomplished by“conduction” of heat from contact with a heat source by placing a rigidor flexible heated element on top of the layers to be sealed with asupporting element below and applying a controlled temperature, pressureand time to complete the seal. Alternatively, carefully controlled hotslitting knives, and “convective” sealing with hot air is used for someapplications such as the production of trash bags and closure of heavywall chemical, fertilizer and bulk food bags. Radiant sealing is veryrare for clear packaging films due to its relative resistance toabsorbing radiant energy and the potential fire hazard of proximity tothe high temperature elements required.

[0007] Virtually all pallet stretch wrapping film is a form of lowdensity polyethylene, typically from 50 gauge to 120 gauge, and the filmis wrapped in multiple layers around the product load. Virtually allheat sealing of the tail of the stretch wrap packaging material to theload is accomplished by “conduction” contact of a heated element.Multiple heated elements are typically arranged to place a series ofseals aligned along the stretch direction to protect the seal from beingpulled apart by the residual force on the film imparted during thewrapping process. Most of the heating elements include some type ofcoating or release material such as Teflon tape to prevent the moltenfilm from sticking to the sealing element. The elements may be appliedto the stationary film or may be rolled on the surface of the wrappedload.

[0008] In the environment where stretch wrappers operate, heat sealinghas been very problematic. Pallet loads may contain a wide variety of“backing” materials to be sealed against, i.e., the material or productsof the load form a backing against which the stretch wrap packagingmaterial is pressed to seal it. Such materials include bulk beveragecontainers, corrugated containers, construction materials includingbrick, stone, and concrete, metal and plastic automotive parts, stacksof paper, and most difficult, irregular loads with substantial voids ofproduct behind the film. As a result of these “backings”, the pressureof the heat sealer often “burns through” the stretch wrap packagingmaterial, resulting in a hole with the potential for product damage fromwater or other contaminants. Loads often do not provide a verticallyplumb side for the sealing element to contact, thereby preventing one ormore of the sealing elements from actually contacting the film.

[0009] Release materials, such as Teflon, used to prevent the film fromsticking to the sealing element eventually wear off and allow film tobuild up on the sealing element. The somewhat delicate heating elementitself may take a beating by repeated contact with the above mentionedloads. This wrapping process can take place in refrigerated, unheatedand even corrosive environments within plants or in the full range ofoutside conditions including temperature and wind. Although a convectivesealing apparatus for stretch wrapping is shown in U.S. Pat. No.4,993,209 to Haloila, the device has not experienced commercial success,most likely due to the types of problems discussed above.

SUMMARY OF THE INVENTION

[0010] Accordingly, the present invention is directed to a method andapparatus for wrapping a load with packaging material which providesadvantages over and obviates several problems associated with earliermethods and apparatus for heat sealing stretch wrap packaging material.

[0011] According to one aspect of the present invention, a heat sealingdevice for sealing plastic film is provided. The heat sealing devicecomprises a heater element; and a sealing head comprising a plurality ofconvection ports, and at least one insulated film contact portionpositioned adjacent at least one of the convection ports and providing aset distance between the convection ports and the plastic film to besealed when in contact with the plastic film.

[0012] According to another aspect of the present invention, a heatsealing device for sealing plastic film includes a heater element, and asealing head comprising a structure having a plurality of convectionports, and an insulated film contact portion positioned adjacent to thestructure and providing a set distance between the convection ports andthe plastic film to be sealed when in contact with the plastic film.

[0013] According to yet another aspect of the present invention, anapparatus for wrapping a load is provided. The apparatus comprises adispenser for dispensing plastic film, a heat sealing device including aheater element and a sealing head, the sealing head comprising aplurality of convection ports and at least one insulated film contactportion positioned adjacent at least one of the convection ports andproviding a set distance between the convection ports and plastic filmon a side of the load when in contact with the plastic film on the sideof the load, and means for providing relative rotation between thedispenser and the load to wrap plastic film around the load.

[0014] According to a further aspect of the present invention, anapparatus for wrapping a load comprises a dispenser for dispensingplastic film, a heat sealing device including a heater element and asealing head, the sealing head comprising a structure having a pluralityof convection ports and an insulated film contact portion positionedadjacent to the structure and providing a set distance between theconvection ports and plastic film to be sealed when in contact with theplastic film to be sealed, and means for providing relative rotationbetween the dispenser and the load to wrap plastic film around the load.

[0015] According to another aspect of the present invention, a method ofwrapping a load with plastic film is provided. The method comprisesplacing a load on a load wrapping surface, providing relative rotationbetween the load and a plastic film dispenser to wrap plastic filmaround the load, pressing a portion of a top layer of the plastic filminto a layer of plastic film below the top layer with at least a portionof a sealing head, and applying a stream of heated air to the portion ofthe top layer of the plastic film from a plurality of convection portsto seal the portion of the plastic film to layer of plastic film belowit, wherein the convection ports are not completely covered by theportion of the plastic film.

[0016] According to yet another aspect of the present invention, amethod of wrapping a load with plastic film comprises placing a load ona load wrapping surface, providing relative rotation between the loadand a plastic film dispenser to wrap plastic film around the load,pressing a portion of a top layer of the plastic film into a layer ofplastic film below the top layer with at least a portion of a sealinghead, and applying a stream of heated air to the portion of the toplayer of the plastic film from a plurality of convection ports to sealthe portion of the plastic film to layer of plastic film below it whilemaintaining the convection ports a set distance from the portion of toplayer of plastic film.

[0017] According to another aspect of the present invention, a method ofwrapping a load with plastic film comprises placing a load on a loadwrapping surface, providing relative rotation between the load and aplastic film dispenser to wrap plastic film around a top of the load anda bottom of the load wrapping surface, extending a top portion of aclamp assembly from below the load wrapping surface, overwrapping thetop portion of the clamp assembly with a top layer of plastic film,pressing a portion of the top layer of the plastic film into a layer ofplastic film below the top layer with at least a portion of a sealinghead, and applying a stream of heated air to the portion of the toplayer of the plastic film from a plurality of convection ports of thesealing head to seal the portion of the plastic film to layer of plasticfilm below it.

[0018] According to a further embodiment of the present invention, anapparatus for wrapping a load comprises means for dispensing plasticfilm, a heat sealing device including a heater element and a sealinghead comprising a plurality of convection ports and means for providinga set distance between the convection ports and plastic film on a sideof the load when in contact with the plastic film on the side of theload, and means for providing relative rotation between the dispenserand the load to wrap plastic film around the load.

[0019] Additional advantages of the invention will be set forth in partin the description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention will be realized and attained by meansof the elements and combinations particularly pointed out in theappended claims.

[0020] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only and are not restrictive of the invention, as claimed.

[0021] The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate several embodimentsof the invention and together with the description, serve to explain theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a side view of an embodiment of a heat sealing apparatusaccording to the present invention;

[0023]FIG. 2 is a side view of another embodiment of a heat sealingapparatus according to the present invention;

[0024]FIG. 3 is a side view of another embodiment of a heat sealingapparatus according to the present invention;

[0025]FIG. 4 is a side view of a further embodiment of a heat sealingapparatus according to the present invention;

[0026]FIG. 5A is a front view of a flexible sealing head of a heatsealing apparatus according to the present invention;

[0027]FIG. 5B is a side view of the heat sealing apparatus of FIG. 5A;

[0028]FIG. 6A is an end view of an embodiment of a heat sealing deviceincorporated into a stretch wrapping apparatus according to the presentinvention;

[0029]FIG. 6B is an end view of an alternative embodiment of the heatsealing device incorporated into a stretch wrapping apparatus accordingto the present invention;

[0030] FIGS. 7-9 are top views of an alternative embodiment of a stretchwrapping apparatus according to the present invention and including theheat sealing device of FIGS. 5A and 5B employed in a method according toone aspect of the invention;

[0031]FIG. 10 is a side view of an alternative embodiment of a stretchwrapping apparatus incorporating the heat sealing device of FIG. 6A;

[0032]FIG. 11 is an end view of the apparatus of FIG. 10;

[0033] FIGS. 12A-12D are end views of the stretch wrapping apparatus ofFIGS. 10 and 11 including the heat sealing device of FIG. 6A employed ina method according to one aspect of the invention;

[0034]FIG. 13A is a front view of heat sealing head having analternative configuration of a standoff insulation element, according tothe present invention;

[0035]FIG. 13B is a side view of the heat sealing head of FIG. 13A;

[0036]FIG. 13C is a front view of another embodiment of a heat sealinghead having an alternative configuration of a standoff insulationelement, according to the present invention;

[0037]FIG. 13D is a side view of the heat sealing head of FIG. 13C;

[0038]FIG. 13E is a front view of another embodiment of a heat sealinghead having an alternative configuration of a standoff insulationelement, according to the present invention;

[0039]FIG. 13F is a side view of the heat sealing head of FIG. 13E;

[0040]FIG. 13G is a front view of another embodiment of a heat sealinghead having an alternative configuration of a standoff insulationelement, according to the present invention; and

[0041]FIG. 13H is a side view of the heat sealing head of FIG. 13G.

DESCRIPTION OF THE EMBODIMENTS

[0042] Reference will now be made in detail to the present embodimentsof the invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

[0043] The present invention provides a method and apparatus forwrapping a load. The apparatus provided substantially reduces theproblems typically associated with heat sealing stretch wrap packagingmaterial. In a preferred embodiment, the present invention allows atleast a portion of a head of the heat sealer to conform to the shape ofthe load, overcoming the difficulties previously posed by irregularloads. In addition, the present invention uses convection and thus doesnot place the heating element in direct contact with the packagingmaterial, thereby preventing the buildup of packaging material on theheating element. Portions of the head of the heat sealer are placed incontact with the packaging material to ensure good contact between thelayers of packaging material to be sealed to one another. These portionsof the heat sealer, defined herein as the “foot” of the heat sealer, areinsulated to prevent them from becoming heated and sticking to thepackaging material.

[0044] In accordance with one aspect of the present invention, an deviceis provided for sealing a trailing (tail) end of packaging material to awrapped load. The device includes a sealing head, a heating element, anda support arm.

[0045] As embodied herein and shown in FIGS. 1, 5A, and 5B, a heatsealing apparatus 100 includes a heating element 150. The heatingelement 150 is contained in a heater box 152. Preferably, the heatingelement 150 is capable of reaching and maintaining a temperature of 700degrees. An air compressor/blower 160 is connected to a first end of theheating box to blow air through the box 152 and over the heating element150. The box 152 may include baffle elements 154 to mix the air flow toensure the air is evenly heated before it leaves the box 152.

[0046] As shown in FIGS. 1, 5A, and 5B, heat sealing apparatus 100includes a flexible sealing head 110. As shown in FIGS. 1, 5A, and 5B,heat sealing head 110 includes a first flexible band 112. First flexibleband 112 includes a plurality of orifices 120 along its length. Thefirst flexible band is preferably made of spring steel, although othermaterials of suitable strength and flexibility may be used. A first endof the first flexible band is attached to a support 114 and a second endof first flexible band 112 is attached to a second support 116. Supports114 and 116 may extend from heater box 150. Alternatively, the ends ofthe band may be directly connected to heater box 150. The first flexibleband 112 is thus formed into a substantially oval-like shape. This ovalshape allows flexible band 112 to flex as it contacts a surface of aload 124. A back face 118 of the first flexible band 112 faces towardheater box such that each orifice 120 is oriented to receive a flexiblehose 126.

[0047] A plurality of flexible hoses 126 extend from an end of theheater box 152 and each flexible hose 126 is in fluid communication withheater box 152 so as to receive the heated air as it passes throughbaffles 154 and out of heater box 152. Each flexible hose 126 isconnected to an orifice 120 in first flexible band 112. Preferably thehoses 126 are connected to flexible band 112 in orifices 120 by snap onpneumatic fittings with brass oval nozzles. Other suitable means ofconnection may be used. Preferably, all of the hoses 126 areapproximately the same length, such that the distance to each orifice120 from the heater box 152 is the same. This ensures that thetemperature of the heated air flowing through each orifice 120 hassubstantially the same temperature. Preferably, the temperature of theair exiting each orifice is between 205 and 240 degrees, and mostpreferably, the temperature of the air is 225 degrees. The temperatureof the air exiting the orifices may vary by approximately ±10 degrees.

[0048] As shown in FIGS. 1, 5A, and 5B, sealing head 110 includes asecond flexible band 130. Second flexible band 130 includes a pluralityof orifices 132 and is attached to a plurality of standoff insulationelements 134. Preferably, the second flexible band 130 is made of a veryflexible material, such as high density polyethylene. Second flexibleband 130 is positioned such that orifices 132 are aligned with orifices120 in first flexible band 112. Thus, together, orifices 120 and 132form a vent to allow heated air to pass from the nozzles of hoses 126.The flexibility of the sealing head 110, imparted by flexible bands 112,130, allows the sealing head to substantially conform to the shape of asurface it contacts, for example a side of the load.

[0049] In one embodiment, a standoff insulation element 134 positionedadjacent each orifice, such that the portions of flexible band 130surrounding orifices 132 are in contact with standoff insulationelements 134. The standoff insulation elements 134 are permanentlyattached to a back face of second flexible band 130.

[0050] The purpose of standoff insulation elements 134 is twofold.First, standoff insulation elements 134 insulate the areas of secondflexible band 130 which do not include an orifice 132. Thus, when theseareas are brought into contact with packaging material, standoffinsulation elements 134 prevent these areas from becoming heated to thehigh temperatures associated with the convective heat sealing air flowand therefore prevents sticking of the insulated areas to the packagingmaterial and thus prevents packaging material from building up on theseareas. As used herein, the term “insulated” simply means that theinsulated material is able to maintain a temperature significantly belowthat of the heated air temperature so as to prevent melting contact withthe packaging material.

[0051] Secondly, standoff insulation elements 134 allow the formation ofthe “vents” between orifices 120 and 132, i.e., elements 134 providespace for air flow between the nozzles in orifices 120 which are blowinghot air and the packaging material onto which the hot air is beingblown. Because there is a distance between the nozzle (orifice 120)through which the hot air is being blown and the packaging materialbeing sealed, a low pressure air flow can be used, reducing thelikelihood that damage will be done to the packaging material. Inaddition, the distance between the nozzle (orifice 120) and thepackaging material prevents the orifice 120 from being completelycovered by packaging material. This is important because if thepackaging material completely covers the orifice 120, it will block airflow and prevent proper sealing of the packaging material. Thus, thestandoff insulation elements are means for providing a set distancebetween the convection ports and plastic film.

[0052] Alternatively, if the packaging material covers the orifice, itwill require a very high pressure to remove the packaging material fromthe orifice, and the pressure may actually puncture the packagingmaterial. Thus, the standoff insulation element 134 should be made froma temperature resistant material, and a material that is fairly rigid toallow a distance to be maintained between the first and second flexiblebands. An example of such a material is ultra-high molecular weightpolyethylene (UHMWPE). If a more compressible material is used, thethickness of the element 134 should be increased to compensate for thecompressibility and to maintain the desired distance between the firstand second flexible bands.

[0053] Although the plurality of standoff insulation elements are shownas positioned between the slits 120, other configurations of standoffinsulation elements may be used as shown in FIGS. 13A-13F. For example,it is possible that the plurality of standoff insulation elements may bereplaced with one or two insulation elements, positioned for example, oneither end of the second flexible band 130 (FIGS. 13C and 13D).Alternatively, it is possible that the standoff insulation elements mayform a frame or mask around a perimeter of the second flexible band 130,enclosing all orifices 120 (FIGS. 13A and 13B). Other suitable designsfor the standoff insulation element, e.g., designs that allow thestandoff insulation element to provide a “cool” surface to press againstthe packaging material and press the layers of packaging materialtogether, and prevent the orifices 120 from becoming blocked with thepackaging material, may also be utilized.

[0054] As shown in FIGS. 1, 5A, and 5B, a front face of each standoffinsulation element 134 is permanently attached to a back face of thesecond flexible band. Any suitable attachment means may be used. A backface of each standoff insulation element 134 includes a bracket likeconfiguration to allow the standoff insulation elements 134 to slidinglyengage a front face 119 of the first flexible band 112, therebyconnecting the first and second flexible bands 112, 130. In a preferredembodiment, one standoff insulation element 134, preferably one locatedin a center of the sealing head 110, is permanently connected to firstflexible band 112. By limiting the fixed connections between the twobands 112, 130, the flexibility of sealing head 110 is enhanced. Thus,the second flexible band 130 is connected to and aligned with the firstband 112 such that the orifices 120, 132 in the first and second bands112, 130 are aligned to form “vents”. Positioned between the first andsecond flexible bands 112, 130 around the orifices 120, 132 are thestandoff insulation elements 134.

[0055] The flexibility of the second flexible band 130 allows the band130 to conform to the shape of a surface 124 a of the load 124 when theheat sealing head 110 is pressed into contact with packaging material onthe surface 124 a of the load 124 during sealing. In addition, thestandoff insulation elements 134 support the flexible band 130 and allowheat sealing head 110 to press the top layer of packaging materialwrapped around the load into contact with a layer directly beneath thetop layer. Because the layers are in contact, they can be sealed to oneanother via the application of hot air through the orifices 120, 132.

[0056] As embodied herein and shown in FIGS. 1, 5A, and 5B, the flexibleheat sealing head 110 is mounted on an arm 140. Arm 140 is movable froma retracted home position to an extended sealing position. Thus, in use,arm 140 extends toward load 124 until heat sealing head 110 is incontact with the packaging material on the side 124 a of the load 124,and remains in contact with the packaging material on the side 124 a ofthe load 124 until heat sealing is performed. After heat sealing, arm140 moves back to the retracted home position, removing heat sealinghead 110 from contact with the packaging material on the load 124.

[0057] As shown in FIGS. 5A and 5B, heat sealing apparatus 100 mayinclude roller bar and hot wire assembly 145. Roller bar and hot wireassembly 145 is preferably mounted on a separate arm 142. Arm 142 ismovable from a retracted home position to an extended sealing andcutting position. Roller bar and hot wire assembly 145 includes a rollerbar 146. Roller bar 146 is preferably mounted in a forward biasedposition on a bar holder 147 (see FIG. 5B). Roller bar 146 is movablewithin bar holder 147 to a rear position. As shown in FIG. 5B, rollerbar 146 is forwardly biased. However, by application of pressure, rollerbar 146 can be moved back until it is in contact with bar holder 147.Roller bar 146 is connected to bar holder 147 such that application ofpressure on only one end of roller bar 146 will cause only that end tomove back toward bar holder 147, such that roller bar 146 would be at anangle with respect to bar holder 147. In use, roller bar 146 is used tomove the packaging material, after wrapping, to a packaging materialholding clamp. Roller bar 146 is also used to push a trailing end of thepackaging material into contact with the load in preparation for heatsealing. After the packaging material is heat sealed to the load, a hotwire 148 (FIG. 5A) is used to cut the packaging material.

[0058] According to another embodiment of the invention, the heatsealing head may comprise a flexible tube. As embodied herein and shownin FIG. 2, a heat sealing device 200 is provided with a flexible heatsealing head 210. Many of the elements present in the previousembodiment are also shown in FIG. 1 and where these elements aresubstantially the same, similar reference numerals have been used and nodetailed description of the element has been provided.

[0059] Heat sealing device 200 includes a heater box 252 containingheater element 250. Flexible heat sealing head 210 is mounted on an arm240 and is movable between a retracted home position and an extendedsealing position. A roller bar and hot wire assembly 245 is alsoprovided.

[0060] Flexible heat sealing head 210 includes a flexible tube 212.Preferably flexible tube 212 is made from a high temperature silicon orTeflon tubing. The tubing may be reinforced with overwound spring orspring steel. Flexible tube 212 is fluid communication with heater box252 to receive the heated air. Flexible tube 212 includes slits or holes220 spaced along its length. Preferably, slits 220 are oval in shape andare spaced approximately 1 and ½ inches apart from one another. Betweenslits 220 are standoff insulating elements 234. Standoff insulatingelements 234 may also be made from portions of a flexible tube. Othersuitable materials and configurations of standoff elements may be used.The purpose of standoff insulating elements 234 is to provide “coldspots” between the seal points on the plastic packaging material, i.e.,to provide places where the flexible sealing head 210 can contact thepackaging material without heating it. By contacting the packagingmaterial, the layers of packaging material to be sealed can be pressedtogether. Additionally, the standoff insulating elements providedistance between the slits 220 and the packaging material to be sealed,allowing room for air flow from the slits 220 to the surface of the load224.

[0061] According to another embodiment of the invention, the heatsealing head may not be flexible. As embodied herein and shown in FIG.3, a heat sealing apparatus is provided with a heat sealing head 310.Many of the elements present in the previous embodiment are also shownin FIG. 3 and where these elements are substantially the same, similarreference numerals have been used and no detailed description of theelement has been provided.

[0062] Sealing head 310 includes a rigid tube 312. Preferably rigid tube312 is made from a high temperature silicon or Teflon tubing. A sealinghead 310 having a rigid tube 312 is useful in applications where theload being wrapped comprises a substantially plumb side or does notinclude irregular shapes. As an alternative to rigid tube 312, a metalnozzle 412 may be used as shown in FIG. 4.

[0063] Rigid tube 312 is in fluid communication with heater box 352 viaa tube 313 to receive heated air. Rigid tube 312 includes slits or holes320 spaced along its length. Preferably, slits 320 are oval in shape andare spaced approximately 1 and ½ inches apart from one another. Betweenslits 320 are standoff insulating elements 334. Standoff insulatingelements 334 may also be made from portions of any type of heatresistant, substantially rigid material. The purpose of standoffinsulating elements 334 is to provide “cold spots” between the sealpoints on the plastic packaging material, i.e., to provide places wherethe rigid sealing head 310 can contact the packaging material withoutheating it. By contacting the packaging material, the layers ofpackaging material to be sealed can be pressed together. Additionally,the standoff insulating elements 334 provide distance between the slits320 and the packaging material to be sealed, allowing room for air flowfrom the slits 320 to the surface of the load.

[0064] As shown in FIG. 4, rigid sealing head 310 may comprise a metalnozzle 412. Metal nozzle 412 is in fluid communication with heater box452 via a tube 413 to receive heated air. Metal nozzle 412 preferablycomprises sheet metal although other suitable materials may be used.Metal nozzle 412 includes baffles 420 for direct air distribution fromheater box 452 to the load. Between baffles 420 are standoff insulatingelements 434. Standoff insulating elements 434 may also be made fromportions of any type of heat resistant, substantially rigid material.

[0065] According to another embodiment of the invention, the heatsealing head may include a heat sealing element unconnected to a foot orstandoff insulation element. As embodied herein and shown in FIGS. 6Aand 6B, a heat sealing device 500 may be configured to be positionedunderneath a load support surface or conveyor wrapping assembly. Heatsealing device 500 includes a heater box (not shown) containing a heaterelement (not shown) as described in previous embodiments.

[0066] The heat sealing device 500 includes a heat sealing head 510.Sealing head 510 includes a heat sealing element such as a rigid tube512. Preferably, rigid tube 512 is made from high temperature silicon orTeflon tubing. Rigid tube 512 is in fluid communication with heater box(not shown) via a tube or other means (not shown) to receive heated air.Rigid tube 512 includes orifices 520 spaced along its length.Preferably, orifices 520 are oval in shape and are spaced approximately1 and ½ inches apart from one another. Rigid tube 512 is positioned suchthat the orifices 520 are facing upward, toward the load supportsurface.

[0067] Rigid tube 512 is connected to and movable with an arm 540. Rigidtube 512 and arm 540 are movable in a horizontal direction, between aretracted position and an extended position. Rigid tube 512 and arm 540may also be movable in a vertical direction, between a lowered,disengaged position and a raised, engaged position.

[0068] As embodied herein, heat sealing device 500 also includes a footor standoff insulation element 534 a. As embodied herein and shown inFIG. 6A, standoff insulation element 534 a is preferably not connectedto rigid tube 512. As shown in FIG. 6A, standoff insulation element 534a is positioned adjacent to rigid tube 512 and is movable independentlyof rigid tube 512. Standoff insulation element 534 a is mounted on asecond arm 540 a, positioned adjacent to arm 540. Standoff insulationelement 534 a and second arm 540 a are movable in a horizontaldirection, between a retracted position and an extended position.Standoff insulation element 534 a and second arm 540 a may also bemovable in a vertical direction, between a lowered, disengaged positionand a raised, engaged position.

[0069] Standoff insulation element 534 a and second arm 540 a arepositioned below a wrapping conveyor assembly 541 and are positionedbetween the heat sealing element (rigid tube 512) with arm 540 and aclamp assembly 561. Clamp assembly 561 includes a top clamp portion 561a and a bottom clamp portion 561 b. Clamp assembly 561 works inconjunction with heat sealing device 500 during the wrapping cycle tosecure and sever the film, as described in detail below.

[0070] Alternatively, as shown in FIG. 6B, standoff insulation element534 b may be positioned above and movable with the heat sealing element(rigid tube 512). As embodied herein, standoff insulation element 534 bmay form a frame or mask in which rigid tube 512 will apply heat to theplastic packaging material. In this embodiment, the standoff insulationelement 534 b is not necessarily positioned between the orifices 520 ofthe rigid tube 512, but instead may form a perimeter around the orifices520 (FIGS. 13A, 13B). Alternatively, standoff insulation element 534 bmay comprise a plurality of “bars” forming standoff portions between theorifices 520 or may comprise “bars” only at the ends of the rigid tube512 (FIGS. 13E and 13F). Any configuration that is sufficient tomaintain “cool” portions to contact and compress the layers of plasticpackaging material together for heat sealing, while keeping the orifices520 free of packaging material, is acceptable. These alternateconfigurations for the standoff insulation element, shown in FIGS.13A-13F and discussed with respect to the first embodiment of the heatsealing apparatus 100 may also be used with the other embodiments of theheat sealing device discussed previously.

[0071] According to another aspect of the invention, a stretch wrappingapparatus including a heat sealing device is provided. The apparatus1000 includes the heat sealing apparatus 100, a packaging materialdispenser, and means for providing relative rotation between thedispenser and the load to wrap packaging material around the load.

[0072] As embodied herein and shown in FIGS. 7-9, the heat sealingapparatus 100 includes a sealing head 110, a heating element 150, and asupport arm 140 as discussed above with respect to FIGS. 1, 5A, and 5B.In addition, a roller bar and hot wire assembly 145 is also preferablyprovided.

[0073] As embodied herein and shown in FIGS. 7-9, stretch wrappingapparatus 1000 includes a packaging material dispenser 102. As shown inFIG. 7, packaging material dispenser 102 dispenses a sheet of packagingmaterial 106 in a web form. Packaging material dispenser 102 includes aroll of packaging material contained within a roll carriage. Packagingmaterial dispenser 102 may be mounted on a stationary mast 105 uponwhich the roll carriage can be vertically positioned to dispensepackaging material from dispenser 102 to wrap load 124 as it rotates.Alternatively, the roll carriage of dispenser 102 may be verticallymoveable on an arm to dispense packaging material 106 spirally aboutload 124 as the arm rotates about load 124 or dispenser 102 may bemounted on a wrapping ring to dispense packaging material 106 spirallyabout load 124 as dispenser 102 rotates around the ring and load 124. Ina preferred embodiment, stretch wrap packaging material is used,however, various other packaging materials such as bubble wrap, netting,strapping, banding, or tape can be used as well. The inventors havefound that the present invention works particularly well when bubblewrap is used as the packaging material. As used herein, the terms“packaging material” and “film” are interchangeable.

[0074] According to one aspect of the invention, the apparatus 1000includes means for providing relative rotation between the dispenser andthe load to wrap packaging material around the load. As shown in FIG. 7,the means for providing relative rotation between the dispenser 102 andthe load 124 may include a motor driven turntable 180 mounted on a baseto rotate load 124 about a vertical axis. The turntable 180 includes aload support surface 186 upon which the load 124 is supported as it iswrapped. In addition, turntable 180 may include conveying means (notshown) for conveying load 124 into and out of the wrapping area.Alternatively, in an arrangement in which packaging material dispenser102 revolves around load 124, the dispenser may be carried by an arm orring or other arrangement. In addition, conveyors 184 a and 184 b may beprovided to move the load to and from the wrapping area, respectively.

[0075] In operation, a method of wrapping a load according to thepresent invention is shown sequentially in FIGS. 7-9. The methodincludes placing the load 124 on a load support surface. Initiatingrelative rotation between the load 124 and a packaging materialdispenser 102 to wrap the packaging material 106 around the load 124while heat sealing device 1000 and roller bar and hot wire assembly 145are in their retracted home positions (FIG. 7).

[0076] As the packaging material 106 is being wrapped around the load124, heater element 150 and air blower 160 of heat sealing device 1000are actuated to allow the heater element 150 to heat up as the load isbeing wrapped and, by actuating the blower, allowing the heated air topass through the heat sealer 1000, warming up all components.

[0077] After the load 124 is wrapped, the heat sealing head 110 androller bar with hot wire assembly 145 move out, for example, byextending or rotating, to contact and distend the packaging material106, moving the packaging material path such that the trailing end ofthe packaging material is positioned over a packaging material clamp(FIG. 8). Once the packaging material is positioned over the clamp, theclamp closes on the packaging material.

[0078] Next, the roller bar and hot wire assembly 145, and heat sealinghead 110 are extended toward the load 124 on arms 142, 140,respectively, until the roller bar 146 locates and contacts a side 124 aof the load 124. (FIG. 9) The heat sealing head 110 continues to advanceinto the side 124 a of the load 124 until the second flexible band ofthe heat sealing head 110 is in contact with packaging material on theside 124 a of the load 124, pushing the top layer of packaging material106 into contact with the layer below it (FIG. 9). While the secondflexible band 130 is in contact with the side 124 a of the load 124, hotair is being blown through the orifices 120, 132 of the heat sealinghead 110 and onto the packaging material 106 that is on the load. Theflexible second band remains in contact with the side 124 a of the load124 for a heat sealing cycle, approximately 2-4 seconds. However, theheating cycle may be longer if necessary or desired.

[0079] After the heat sealing is complete, the hot wire cuts thepackaging material, and the roller bar and hot wire assembly 145 andheat sealing head 110 are withdrawn from the side 124 a of the load, andthen move back to the home position. The blower 160 and heater element150 shut off after the heat sealing cycle is complete.

[0080] In an alternative embodiment of a stretch wrapping apparatus andaccording to one aspect of the invention, a wrapping conveyor 707 havinga top load support surface and a bottom packaging material transfersurface is provided instead of a turntable.

[0081] As embodied herein and shown in FIGS. 10-12D, a ring stretchwrapping apparatus 700 is provided. Apparatus 700 includes a feedconveyor 703, a wrap and load conveyor assembly 707, a packagingmaterial dispensing mechanism 702 with a cutting mechanism (not shown),a take off conveyor 711, and a heat sealing device 710 (as describedpreviously with respect to FIGS. 6A and 6B).

[0082] The load 724 is placed on an infeed conveyor 703 which includesan endless belt 756 mounted on a frame support 758. The endless belt 756is mounted on rollers 760 which are rotatably journaled by suitablebearing means and brackets which are secured to the frame support 758.The infeed conveyor 703 carries the load 724 onto a wrapping station 741including a packaging material dispensing apparatus 702 and a wrappingconveyor assembly 707.

[0083] The wrapping assembly includes a frame 762 on which a steel donutor ring shaped packaging material support member 764 is rotatablymounted and supported on three planes by guide rollers 766. If desired,the packaging material support member 764 can be constructed ofaluminum. A plurality of guide rollers 766 project inward from the frame762 on arms 767 and mounting plates 768 to engage the ring shaped member764 so that it can be driven in a predetermined path. A friction drivewheel 769 is positioned adjacent the ring member 764 at its base andengages the member 764 to rotate the member 764 within the guide wheelrolling area. The friction drive wheel 769 is driven by a motor 770having a shaft that is suitably connected with a drive reducer 772.Material roll dispensing shaft 774 is rotatably secured to the ringmember 764 for rotation on its axis and is adapted to receive and hold aroll of packaging material 776.

[0084] The wrapping conveyor assembly 707 comprises two conveyingsurfaces 782 and 784. The top load supporting and conveying surface 782is a standard plate type conveyor well known in the art comprising adriven endless belt 786 mounted on a plurality of rollers 790. Therollers 790 are supported by plates 792 secured in turn to a framemember (not shown) which holds the rollers in a rotatable position. Theendless belt 786 is rotated in a direction which moves anything on thebelt 786 through the wrapping device 741 in a direction forming from theinfeed conveyor 703 toward the take-off conveyor 711. Belt 786 is drivenby a motor assembly 794 which is connected by gears 796 and linkages 798in the form of chains or belts to drive the conveyor.

[0085] Lower packaging material transporting conveyor 784 is anon-driven conveyor and includes two sets of inline rollers 794 a and794 b mounted to an outer surface of a rail (not shown) on either sideof a conveying surface of conveyor 782. These rollers are inlinedirectly one behind the other to form two rows of rollers. Non-drivenrollers 794 a, 794 b are preferably roller skate wheels, approximatelytwo inches in diameter, aligned in an inline configuration. Other sizesor types of wheels may be used, however, currently preferred are rollerskate wheels, which are inexpensive, easy to find, of the appropriatesize, and commonly used in carton conveyors. Alternatively, more thantwo rows of rollers may be used, or only a single row of rollers may beused. In an alternative embodiment, the lower packaging materialtransporting conveyor 784 may be driven (motorized) by any suitablemeans, and the surface may comprise, for example, driven rollers or anendless driven belt.

[0086] This construction of the wrapping conveyor assembly 707 allowspackaging material 778 to be wrapped around a load 724 which was carriedfrom the infeed conveyor 703 onto the wrapping station 741. Thepackaging material 778 is wrapped around the wrapping conveyor assembly707 and the load 724 with both the load 724 and packaging material 778being carried by the conveyor assembly 707 in the same direction. In allwrapping modes—full web, spiral and banding modes—the conveyor assembly707 and wrapping ring 764 are stopped and the heat sealing device 710and clamp apparatus 761 work together to clamp, heat seal, and sever thepackaging material. The heat dispensing portion is mounted on anextendable arm 740, and positioned near clamp assembly 761. Betweenclamp assembly 761 and heat dispensing portion, standoff insulationelement 734 a is mounted on extendable arm 740 a. The conveyor assembly707 is activated carrying the load and wrap downstream to a takeoffconveyor 711. When the load 724 encounters the takeoff conveyor 711, theelongated stretched wrap 778 coming off the end of the conveyor assemblyover last inset rollers 794 c, 794 d assumes its memory position Magainst the load in the space between the conveyor assembly 707 andtakeoff conveyor 711, allowing the contained load covered by stretchwrap to be carried away.

[0087] The wrapping conveyor assembly 707 leads from the infeed conveyor703 to a takeoff conveyor 711 which is constructed like the infeedconveyor 703 and runs at the same speed as the infeed conveyor 703. Inorder to control both conveyors at the same rate of speed, a suitablemechanical means not shown is set up to make the drive of both theinfeed conveyor 703 and the takeoff conveyor 711 equal to reductiongearing assembly of the drive motor. Thus, if the motor slows down orspeeds up to drive the wrapping mechanism at different speeds, theinfeed and takeoff conveyors simultaneously speed up or slow down sothat the load moves to conveyor assembly 707 and is taken away from theconveyor assembly 707 at consistent relative speeds.

[0088] A method for wrapping a load according to the second embodimentof the present invention will now be described. In the operation of theinventive wrapping apparatus, full web, spiral web, and banding modes ofoperation are substantially identical manner. In these modes, a feedconveyor 703 brings the load 724 onto the top load supporting andconveying surface 782 of wrapping conveyor assembly 707. Load supportingand conveying surface 782 then carries the load to a predetermined wrapposition within the packaging material dispensing path and the conveyorassembly stops leaving the load in a stationary position.

[0089] A leading edge 777 of the packaging material 778 is held in aclamping assembly 761 located beneath the conveyor assembly 707 as seenin FIGS. 10 and 11. After at least one wrap has been made around theload 724 and the clamp assembly 761, the clamps 761 a, 761 b are rotatedreleasing edge 777 which is held by the web wrap. If the wrap is for afull web load or a banded load, a plurality of overlying layers ofpackaging material are wrapped around the load and the conveyor assembly707. In the spiral wrap mode, a plural number of wraps are wrappedaround the downstream end of the load 724 in the same manner as thebanding and the conveyor assembly is activated carrying the loaddownstream to a takeoff conveyor so that a spiral wrap is formed aroundthe load.

[0090] When the load 724 reaches a station where the end is sensed by afeeler gauge, light sensing means, pressure sensor switch or othersuitable sensing mechanism, both the takeoff conveyor 711 and thewrapping conveyor assembly 707 stop and a second band is placed aroundthe upstream end of the load 724 in the same manner as if a band or fullweb wrap were being wrapping around the load 724.

[0091] Before completion of the wrap cycle, a top clamp portion 761 a ofthe clamp assembly 761 extends outward from below conveyor assembly,allowing at least the last layers of the packaging material wrap to besupported between the edge of the conveyor assembly 707 and the topclamp portion 761 a (FIG. 12A). After top clamp portion 761 a extendsout and is overwrapped by the packaging material, standoff insulationelement 734 a and heat sealing element (rigid tube 712 with orifices720) of the heat sealing device 710 extend out from beneath the conveyorassembly 707 on arms 740 a, 740, respectively. Standoff insulationelement 734 a engages the packaging material 778 and pushes the lastlayer upward, into contact with the layers beneath it (FIG. 12B). Oncethe layers of packaging material are pushed into contact with oneanother, hot air is blown through rigid tube 712 and orifices 520 ontothe layers of packaging material. The sealing cycle lasts forapproximately 2-4 seconds, although it may be longer if necessary. Afterthe sealing cycle and a short cooling period, approximately 2-5 seconds,the lower clamp portion 761 b of the clamp assembly 761 extends outward,clamping the packaging material web between the top and bottom clampportions 761 a, 761 b of the clamp assembly 761, cutting the packagingmaterial web and clamping the leading edge of the packaging material forthe next wrap cycle (FIG. 12C). The heat sealer device 710 thenwithdraws under the wrapping conveyor assembly as the load 724 exits thewrapping area (FIG. 12D).

[0092] Alternatively, when a heat sealing device 710 that does notinclude separately mounted standoff insulation and sealing elements(FIG. 6B), the method is substantially the same. After top clamp portion761 a extends and is overwrapped, the heat sealing element 712 with theconnected standoff insulation element 734 b extend out from beneath thewrapping conveyor assembly 707 in a lowered position. The heat sealingelement 712 and standoff insulation element 734 b are then raised intothe engaged position, such that the standoff insulation element 734 bcontacts the packaging material 778 and presses the layers of thepackaging material together. The heating cycle is actuated, and aftercooling, the lower clamp 761 b portion of the clamp assembly 761 extendsout to clamp and cut the packaging material 778. The heat sealingelement 712 and standoff insulation element 734 b are lowered to thedisengaged position and withdrawn while the load 724 exits the wrappingarea.

[0093] The method and device for sealing plastic wrap taught herein canbe used in processes other than stretch wrapping, where it is necessaryto seal together layers of packaging material, especially when thelayers of packaging material should be compressed prior to sealing.Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

what is claimed is:
 1. A heat sealing device for sealing plastic film,comprising: a heater element; and a sealing head comprising: a pluralityof convection ports; and at least one insulated film contact portionpositioned adjacent at least one of the convection ports and providing aset distance between the convection ports and the plastic film to besealed when in contact with the plastic film.
 2. The device of claim 1,wherein the sealing head is sufficiently flexible such that the sealinghead substantially conforms to a surface that it contacts.
 3. The deviceof claim 1, wherein the insulated film contact portion is configured topress a top layer of plastic film into a lower layer of plastic film. 4.The device of claim 1, wherein the sealing head is sufficiently rigidsuch that the sealing head does not conform to a surface that itcontacts.
 5. The device of claim 1, wherein the sealing head furthercomprises a first flexible band and a second flexible band.
 6. Thedevice of claim 5, wherein the at least one insulated film contactportion is positioned between the first and second flexible bands. 7.The device of claim 1, further comprising a plurality of hoses extendingbetween the heater element and the plurality of convection ports.
 8. Thedevice of claim 7, wherein a separate hose is provided for eachconvection port.
 9. The device of claim 7, wherein the hoses areflexible.
 10. The device of claim 1, wherein the sealing head furthercomprises a rigid tube with a plurality of orifices forming theconvection port.
 11. The device of claim 10, wherein a plurality ofinsulated film contact portions are provided.
 12. The device of claim11, wherein the plurality of insulated film contact portions arepositioned between the convection ports.
 13. The device of claim 10,wherein the at least one insulated film contact portion is a barextending along the length of the tube and adjacent the convectionports.
 14. The device of claim 10, wherein the at least one insulatedfilm contact portion is a frame surrounding an outer perimeter of theconvection ports.
 15. The device of claim 10, further comprising twoinsulated film contact portions, each portion being positioned on an endof the rigid tube and adjacent a convection port.
 16. The device ofclaim 1, wherein the sealing head further comprises a flexible hose witha plurality of orifices forming the convection ports.
 17. The device ofclaim 16, wherein a plurality of insulated film contact portions areprovided.
 18. The device of claim 17, wherein the plurality of insulatedfilm contact portions are positioned between the convection ports. 19.The device of claim 18, wherein the plurality of insulated film contactportions are rings.
 20. The device of claim 16, wherein the at least oneinsulated film contact portion is a frame, surrounding an outerperimeter of the convection ports.
 21. The device of claim 1, whereinthe sealing head is a metal nozzle including a plurality of orificesforming the convection ports.
 22. The device of claim 21, including aplurality of insulated film contact portions.
 23. The device of claim22, wherein the plurality of insulated film contact portions arepositioned between the convection ports.
 24. The device of claim 1,wherein the heat sealing head is mounted on and movable with an arm. 25.The device of claim 1, further comprising a roller bar and hot wireassembly.
 26. A heat sealing device for sealing plastic film,comprising: a heater element; and a sealing head comprising: a structurehaving a plurality of convection ports; and an insulated film contactportion positioned adjacent to the structure and providing a setdistance between the convection ports and the plastic film to be sealedwhen in contact with the plastic film.
 27. The device of claim 26,wherein the structure having a plurality of convection ports is mountedon and movable with a first arm.
 28. The device of claim 27, wherein theinsulated film contact portion is mounted on and movable with a secondarm.
 29. The device of claim 28, wherein the insulated film contact isconfigured to press a top layer of plastic film into a lower layer ofplastic film.
 30. The device of claim 26, wherein the structure is arigid tube.
 31. An apparatus for wrapping a load, comprising: adispenser for dispensing plastic film; a heat sealing device including aheater element and a sealing head comprising a plurality of convectionports and at least one insulated film contact portion positionedadjacent at least one of the convection ports and providing a setdistance between the convection ports and plastic film on a side of theload when in contact with the plastic film on the side of the load; andmeans for providing relative rotation between the dispenser and the loadto wrap plastic film around the load.
 32. The apparatus of claim 31,wherein the sealing head is sufficiently flexible such that the sealinghead substantially conforms to a surface that it contacts.
 33. Theapparatus of claim 31, wherein the sealing head is sufficiently rigidsuch that the sealing head does not conform to a surface that itcontacts.
 34. The apparatus of claim 31, wherein the insulated loadcontact portions are configured to press a top layer of plastic wrap toa layer below it.
 35. The apparatus of claim 31, further comprising aplurality of hoses extending between the heater element and theconvection ports of the sealing head.
 36. The apparatus of claim 35,wherein the hoses are flexible.
 37. The apparatus of claim 35, whereineach of the hoses has a length and the lengths of the hoses are thesame.
 38. The apparatus of claim 35, further comprising a plurality ofinsulated film contact portions positioned between the convection ports.39. The apparatus of claim 31, wherein the means for providing relativerotation is a turntable.
 40. The apparatus of claim 31, wherein themeans for providing relative rotation is a wrapping ring upon which thedispenser is mounted.
 41. The apparatus of claim 31, wherein the sealinghead is mounted on and movable with an arm.
 42. The apparatus of claim31, wherein the sealing head further includes a first flexible band anda second flexible band.
 43. The apparatus of claim 42, wherein the atleast one insulated film contact portion is positioned between the firstand second bands.
 44. The apparatus of claim 43, wherein a plurality ofinsulated film contact portions are provided, and wherein the insulatedfilm contact portions are positioned between the first and second bands.45. The apparatus of claim 44, wherein each of the first and secondbands includes a plurality of orifices, and wherein the orifices of thefirst band are aligned with the orifices of the second band.
 46. Theapparatus of claim 45, wherein the plurality of insulated film contactportions are positioned between the orifices of the first and secondbands to form a plurality of vents for the convection ports.
 47. Theapparatus of claim 31, further comprising a roller bar and hot wireassembly.
 48. The apparatus of claim 47, wherein the sealing head ismounted on and movable with a first arm.
 49. The apparatus of claim 48,wherein the roller bar and hot wire assembly is mounted on and movablewith a second arm.
 50. The apparatus of claim 31, wherein the sealinghead includes a rigid tube with a plurality of orifices forming theconvection ports.
 51. The apparatus of claim 50, wherein the at leastone insulated film contact portion is a bar extending along the lengthof the tube and adjacent the orifices of the tube.
 52. The apparatus ofclaim 50, including a plurality of insulated film contact portions. 53.The apparatus of claim 52, wherein the plurality of insulated filmcontact portions are positioned between the orifices of the rigid tube.54. The apparatus of claim 31, wherein the sealing head includes aflexible hose with a plurality of orifices forming the convection ports.55. The apparatus of claim 54, wherein a plurality of insulated filmcontact portions are provided.
 56. The apparatus of claim 55, whereinthe plurality of insulated film contact portions are positioned betweenthe orifices of the flexible hose.
 57. The apparatus of claim 56,wherein the plurality of insulated film contact portions are rings of aninsulating material surrounding the flexible hose.
 58. The apparatus ofclaim 40, further comprising a wrapping conveyor assembly for supportingand transporting the load.
 59. The apparatus of claim 58, wherein thesealing head is positioned beneath the wrapping conveyor assembly. 60.The apparatus of claim 59, wherein the sealing head is movable on an armbetween a retracted position beneath the wrapping ring and an extendedposition beyond the wrapping ring.
 61. The apparatus of the 59, whereinthe sealing head is positioned such that the convection ports face anunderside of the wrapping conveyor assembly.
 62. The apparatus of claim59, wherein the sealing head is a rigid structure including a pluralityof orifices forming the convection ports.
 63. The apparatus of claim 62,wherein the at least one insulated film contact portion extends along alength of the rigid structure.
 64. The apparatus of claim 63, whereinthe sealing head is moveable between a raised engaged position and alowered, disengaged position.
 65. The apparatus of claim 64, wherein theat least one insulated film contact portion is engagable with plasticfilm wrapped around the load and the underside of the wrapping conveyorassembly when the sealing head is in the raised, engaged position. 66.The apparatus of claim 59, further comprising a plastic film clampassembly.
 67. An apparatus for wrapping a load, comprising: a dispenserfor dispensing plastic film; a heat sealing device including a heaterelement and a sealing head comprising a structure having a plurality ofconvection ports and an insulated film contact portion positionedadjacent to the structure and providing a set distance between theconvection ports and plastic film to be sealed when in contact with theplastic film to be sealed; and means for providing relative rotationbetween the dispenser and the load to wrap plastic film around the load.68. The apparatus of claim 67, wherein the means for providing relativerotation is a wrapping ring having the dispenser mounted thereon. 69.The apparatus of claim 68, further comprising a wrapping conveyorassembly for supporting and transporting the load during wrapping. 70.The apparatus of claim 69, wherein the sealing device is positionedbelow the wrapping conveyor assembly.
 71. The apparatus of claim 70,wherein the structure is a rigid tube.
 72. The apparatus of claim 71,wherein the rigid tube is mounted on and movable with a first arm. 73.The apparatus of claim 72, wherein the insulated film contact portion ismounted on and movable with a second arm.
 74. The apparatus of claim 73,further comprising a film clamping assembly.
 75. The apparatus of claim74, wherein the insulated film contact portion is positioned between therigid tube and the film clamping assembly.
 76. The apparatus of claim75, wherein the convection ports are oriented to face an underside ofthe wrapping conveyor assembly.
 77. The apparatus of claim 67, whereinthe insulated film contact is configured to press a top layer of plasticfilm into a lower layer of plastic film.
 78. A method of wrapping a loadwith plastic film, comprising: placing a load on a load wrappingsurface; providing relative rotation between the load and a plastic filmdispenser to wrap plastic film around the load; pressing a portion of atop layer of the plastic film into a layer of plastic film below the toplayer with at least a portion of a sealing head; and applying a streamof heated air to the portion of the top layer of the plastic film from aplurality of convection ports to seal the portion of the plastic film tolayer of plastic film below it, wherein the convection ports are notcompletely covered by the portion of the plastic film.
 79. The method ofclaim 78, wherein providing relative rotation includes actuating aturntable upon which the load is supported.
 80. The method of claim 78,wherein providing relative rotation includes rotating the dispenseraround the load on a wrapping ring.
 81. The method of claim 78, whereinpressing a portion of the top layer of the plastic film into a layer ofplastic film below the top layer includes pressing the portion of thetop layer of plastic film into a side of the wrapped load.
 82. Themethod of claim 81, wherein pressing the portion of the top layer ofplastic film into a side of the wrapped load includes moving the sealinghead to intercept the plastic film extending between the load and thedispenser.
 83. The method of claim 82, wherein pressing the portion ofthe top layer of plastic film into a side of the wrapped load furtherincludes contacting the portion of the top layer of plastic film with atleast one insulated film contact portion.
 84. The method of claim 83,wherein the at least one insulated film contact portion distances theconvection ports from the portion of the top layer of plastic film. 85.The method of claim 78, further comprising clamping the top layer ofplastic film.
 86. The method of claim 78, further comprising severingthe top layer of plastic film.
 87. The method of claim 86, whereinsevering the top layer of plastic film includes engaging the top layerof plastic film with a roller bar and hot wire assembly.
 88. The methodof claim 78, wherein pressing a portion of the top layer of the plasticfilm into a layer of plastic film below the top layer includes extendinga top clamp portion from beneath a wrapping conveyor assembly.
 89. Themethod of claim 88, wherein pressing a portion of the top layer of theplastic film into a layer of plastic film below the top layer furtherincludes overwrapping the top claim portion with the top layer ofplastic film.
 90. The method of claim 89, wherein pressing a portion ofthe top layer of the plastic film into a layer of plastic film below thetop layer further includes contacting the portion of the top layer withat least one insulated film contact portion.
 91. The method of claim 89,wherein contacting the portion of the top layer with at least oneinsulated film contact portion includes extending the at least oneinsulated film contact portion outward from beneath the wrappingconveyor assembly.
 92. The method of claim 90, wherein contacting theportion of the top layer with at least one insulated film contactportion further includes moving the at least one insulated film contactportion upward to push the portion of the top layer of plastic film intothe layer of film below it.
 93. The method of claim 92, wherein the atleast one insulated film contact portion distances the convection portsfrom the portion of the top layer of plastic film.
 94. A method ofwrapping a load with plastic film, comprising: placing a load on a loadwrapping surface; providing relative rotation between the load and aplastic film dispenser to wrap plastic film around the load; pressing aportion of a top layer of the plastic film into a layer of plastic filmbelow the top layer with at least a portion of a sealing head; andapplying a stream of heated air to the portion of the top layer of theplastic film from a plurality of convection ports to seal the portion ofthe plastic film to layer of plastic film below it while maintaining theconvection ports a set distance from the portion of top layer of plasticfilm.
 95. A method of wrapping a load with plastic film, comprising:placing a load on a load wrapping surface; providing relative rotationbetween the load and a plastic film dispenser to wrap plastic filmaround a top of the load and a bottom of the load wrapping surface;extending a top portion of a clamp assembly from below the load wrappingsurface; overwrapping the top portion of the clamp assembly with a toplayer of plastic film; pressing a portion of the top layer of theplastic film into a layer of plastic film below the top layer with atleast a portion of a sealing head; and applying a stream of heated airto the portion of the top layer of the plastic film from a plurality ofconvection ports of the sealing head to seal the portion of the plasticfilm to layer of plastic film below it.
 96. The method of claim 95,further comprising extending a bottom portion of the clamp assembly frombelow the load wrapping surface.
 97. The method of claim 96, furthercomprising severing the top layer of the plastic film.
 98. The method ofclaim 95, wherein pressing a portion of the top layer of the plasticfilm into a layer of plastic film below the top layer includescontacting the portion of the top layer with at least one insulated filmcontact portion.
 99. The method of claim 98, wherein contacting theportion of the top layer with at least one insulated film contactportion includes extending the at least one insulated film contactportion outward from beneath the load support surface.
 100. The methodof claim 99, wherein contacting the portion of the top layer with atleast one insulated film contact portion further includes moving the atleast one insulated film contact portion upward to push the portion ofthe top layer of plastic film into the layer of film below it.
 101. Themethod of claim 100, wherein the at least one insulated film contactportion distances the convection ports from the portion of the top layerof plastic film.
 102. An apparatus for wrapping a load, comprising:means for dispensing plastic film; a heat sealing device including aheater element and a sealing head comprising a plurality of convectionports and means for providing a set distance between the convectionports and plastic film on a side of the load when in contact with theplastic film on the side of the load; and means for providing relativerotation between the dispenser and the load to wrap plastic film aroundthe load.